With the ignominious collapse of the Republican effort to repeal and replace the Affordable Care Act, some observers are already talking about a crippled Trump administration. The health-care failure will force a far more modest approach to tax reform than originally planned, the thinking goes, and Trump's trillion-dollar infrastructure plan will collapse for similar reasons. With palpable glee, headlines are being written about a "fiery civil war" within the GOP.

In this context, let's dust off political scientist Corey Robin's influential essay articulating an extended analogy between the then-incoming Trump administration and the administration of Jimmy Carter.

Carter was what Robin calls a "disjunctive president," someone who leads a coalition that was once dominant but is now in the late stages of fragmentation. The disjunctive leader's aim is to reorient that coalition around the novel challenges of that political moment, and thereby to restore their coalition to primacy. But he's unable to herd the necessary cats, and is therefore succeeded by a "reconstructive" president, someone who is capable of articulating that response and following through with action, in part because he needs a new coalition more naturally built around that response.

At the time the article was written, there were already potent reasons to find this Trump-Carter analogy plausible, in spite of the wild differences in personality and ideology between the two presidents. Both Carter and Trump ran as outsiders to the established power structure of their parties, and faced fierce resistance from the old guard. Both ran on heterodox programs and scrambled what had been traditional electoral coalitions, and both won very narrowly. The increasing friction between the White House and the GOP congressional leadership further confirms the analogy, as does the planned shift to "easy victories" over taxes. As Robin wrote back in January:

One of the signature promises of the Trump campaign is already turning into a curse.

Where all this will lead is anyone's guess, but the most likely outcome is that Trump and the GOP will fall back on what Republicans know how to do best: tax cuts and deregulation. At moments of articulation, holding fast to the regime's orthodoxies can be intoxicating sources of power, as Lyndon Johnson and George W. Bush learned. At moments of disjunction, that kind of steadfastness can lead to disaster. [Corey Robin]

But there's a problem with the analogy: Plenty of observers at the time thought the 2008 election ushered in a "reconstructive" presidency and a new dispensation. Those hopes were bitterly disappointed — beginning with disappointment that the best health-care bill the Democrats could pass was the insurer-friendly Affordable Care Act. And today, the possibilities that Robin articulates depend on a factor that at least in 2008 was present but now — so far, at least — is absent. That is a "reconstructive" figure poised for triumph on the Democratic side.

Well, actually, there's one obvious possibility:

So now that everyone seems to be coming around to Trump as Jimmy Carter, it's time to ponder ... Bernie Sanders as Ronald Reagan.

As Douthat points out, Sanders ran an insurgent campaign against Hillary Clinton much as Reagan ran against Gerald Ford in 1976. And Sanders represents a throwback to an earlier form of unapologetic big-government liberalism that had been largely repudiated after the Mondale debacle in 1984, just as Reagan represented a throwback to an earlier form of anti-government conservatism that had been largely repudiated after the Goldwater debacle in 1964.

Otherobservers have noted Sanders' ability to speak successfully to Trump voters and their concerns, and asked why the Democrats aren't embracing a populist politics of their own, redeeming the very promises on which Trump himself will be unable to deliver.

But the fact is: They aren't. And even Bernie Sanders isn't — not really. Which is why he isn't really the Democratic Reagan.

The opposition to the GOP's American Health Care Act wasn't particularly organized by the Democratic leadership; it sprang from a combination of the true grassroots and a variety of ideological and interest groups. The Democratic Party as a whole hasn't yet figured out how to capitalize on such a glaring and obvious failure. And while more progressive insurgents are pushing an agenda, it's not the right one for capitalizing on the AHCA debacle.

In the wake of the AHCA's failure, there has been an increase in support for a single-payer system, largely in safe Democratic areas. But Donald Trump didn't win the presidency because he promised a better deal than ObamaCare, and single-payer — even if it's a good idea — isn't going to be the banner under which the Democrats can plausibly bring a new coalition to dominance, because ultimately it would be just that: a good idea. The Democrats have never lacked for individual ideas that poll well or have serious policy work behind them. That's not their most fundamental problem.

Disjunctive presidents have a genuine grasp of some essential aspects of the crisis the nation faced and how it threatened their governing coalition. They ask some of the most important and correct questions in their campaigns, which is why they are able to win, and their only hope of success is in addressing those questions correctly.

Carter paved the way for Reagan when he ran in opposition to school busing and courted the newly awakened white evangelical vote; when he championed deregulation of finance and the airlines; when he appointed Paul Volcker to the Fed; and when he responded to the Soviet invasion of Afghanistan. Reagan did not win the presidency by saying Goldwater's libertarian, fiercely anti-communist conservatism was the eternal truth (which, to be fair, is pretty much what he did say when he supported Goldwater in 1964). Rather, he said that in the "present crisis" government was the problem rather than the solution.

The populist explanation for that crisis is the devouring of the public weal by special interests — and left- and right-wing populists mostly disagree on which interests to blame. But the promise to restore that ladder to prosperity is what got Trump elected. The Democrats need a champion who can redeem that promise — which there is every reason to expect Trump cannot deliver on.

There may or may not be a place for championing single-payer health care as part of that message. The last thing the Democrats need is to be scared of their own shadow when it comes to big, apparently unlikely initiatives, and under a big umbrella there will be room for dozens if not hundreds of policy ideas, some of which will barely cohere. But the big idea under which all those policies cohere must be a response to that central crisis, that explains why we no longer have a broadly shared prosperity and how to restore it.

When the Democrats have found their "reconstructive" Reagan — whether it's Sanders or someone who inherits his banner — it'll be obvious, because he or she will talk as he did, and articulate how in the present crisis their philosophy will be responsive.